Mobile overhead service unit



May 5, 1970 M ;VE. MITCHELL Y 3,509,965

MOBILE OVERHEAD SERVICE UNIT Filed Sept. 13, 196e 4 sheets-sheet 1 l lg i I I I Il I l il ,I -'s ;l 1jrv al INVENTOR.

MAURICE E. MITCHELL ATTORNEYS May 5, 1970 E, MITCHELL 3,509,965 I MOBILE OVERHEAD SERVICE UNIT Filed sept. 13, 196e 4 sheets-#sheet 2 INVENTOR MAURICE E. MITCHELL ATTORNEYS May 5, 1970 M. E. MITCHELL 3,509,965

MOBILE OVERHEAD SERVICE UNIT Filed Sept. 13, 1968 4 Sheets-Sheet 3 Fig.

INVENTOR. MAURICE E. MITCHELL ATTORNEYS May 5, 1970 l M..l l; MITCHELL '3,509,965

MOBILE OVERHEAD sERvIcE UNIT Enea sept. 13, 196e 4 sheets-sheet 4l Eig. 8

INVENTOR. MAURICE E. MITCHELL ATTORNEYS United States Patent O U.S. Cl. 182-62.5 8 Claims ABSTRACT OF THE DISCLOSURE This compact overhead service unit has an elongated traversing work platform mounted on a lift mast carried, with a counter-balance, on a turntable in a self-propelled mobile base. The elongated platform has a centered travel position wherein it is lowered over the mast, which then projects through a trap door in the platform, in a highly compact arrangement for travel through restricted aisles and doorways under control of a workman on the lowered platform. Power is supplied from a battery mounted in counter-balance relation on the turntable. One lift cylinder raises the platform carrier to the top of the mast assembly. A second lift cylinder extends the mast to raise the platform to any level up to an extreme top position. Turntable rotation swings the platform continuously through 360 in either direction at any level. The platform can be traversed horizontally and radially outward to an extreme reach position in any direction at any level above the lowered mast, and in extended position can be lowered below the top of the mast and swung. The unit thus combines extreme travel compactness with versatile work positioning over a large swing area and great lift height from a stationary mobile base in a restricted area.

This invention is an improvement of the overhead service unit shown in my prior Pat. No. 2,787,278 dated Apr. 2, 1957.

This invention relates to a mobile overhead service unit for use in performing construction and maintenance operations in elevated positions. It is useful in cleaning, re-lamping, and repairing overhead light fixtures and in other construction and maintenance service in the interior of industrial, commercial, and like buildings. It is also useful in various other construction and maintenance operations which are required to be performed in elevated positions, especially in the construction and overhaul and servicing of aircraft.

It is a special object of the present invention to provide a mobile service unit which will have a small and compact travel condition, so that it can move freely through interior halls and doorways and through narrow aisles of a crowded factory area; and will have a work platform which from a stationary position of the mobile base will be extensible horizontally between a retracted position and a relatively extreme outward reach in any direction at any level up to a high elevation above the base.

The overhead service unit of the present invention utilizes a low mobile base like that of my prior Pat. No. 3,095,945, having driven rear wheels and steerable front wheels, with the base formed to define a large well in which a turntable is mounted at a low level. The turntable carries a mast which supports the work platform and also carries a power-source battery in counter-balance relation with the platform, and carries control mechanism and switches by which the unit can be driven between work locations by a workman on the lowered platform and by which the platform can be raised and the turntable swivelled as desired.

In accordance with the present invention, the mast is a multiple-section vertical mast which is extensible by actuation of its own hydraulic cylinder. The platform is mounted on a carrier which is movable vertically along the outer face of the top section of the mast and is actuated by its own separate cylinder so that it can be raised and lowered along the top section independently of the mast operation. By this means, the platform carrier can be raised to a position in which the platform clears the top of the mast and can be traversed on its carrier outward from its centered position to an extreme reach position beyond the periphery of the base. The traversingplatform is of substantial length to provide a long reach beyond the area of the base. With the platform retracted to its centered position and lowered over the upstanding mast and drive controls to travel position, the unit has a sufliciently low height to pass through door openings and under low overhead obstructions, and has a compact arrangement which permits it to travel along narrow aisles and to negotiate restricted turns. At a work location, the platform can be turned with the turntable to any direction, and when once raised to mast-clearing position, can be extended horizontally outward at any level to which it is lifted by the mast. It is a special advantage that the platform can thus be extended horizontally outward in any direction at any level up to a high level above the base without moving the base. In extended position the platform can also be lowered to a Working level contiguous to that which can be reached from the door, and can be swung to any direction at that level. The unit thus provides uniquely versatile working access to overhead service positions, at any point in a large volume of space.

By way of example, a unit which retracted position has a maximum horizontal dimension of less than eight feet and a clearance height less than nine feet, the platform can be swung to cover any point in a 20 foot diameter circle, can be positioned at any working level from a low level of five feet, four inches, to a top level of 28 feet, and can be extended horizontally in any direction at any level above the retracted mast.

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a side elevation of a mobile overhead service unit embodying the invention, with its platform in retracted travel position;

FIG. 2 is a front elevation of the unit shown in FIG. 1, with the turntable swung and the platform raised to mast-clearing position and traversed to its extreme reach position, showing in dotted lines the extreme lowered and elevated positions of the platform in this extended relation; l

F IG. 3 is a plan view of the unit shown in FIG. 2;

FIG. 4 is a vertical sectional view, taken longitudinally of the platform and showing the mounting of the traversing platform on the platform carrier;

FIG. 5 is a transverse section taken on the line 5-5 of FIG. 4;

FIG. 6 is a horizontal section taken on the line 6 6 of FIG. 2, showing the relationship of the mast to the turntable, and of the mast sections to each other and to the platform carrier;

FIG. 7 is a diagrammatic view of the mast in partially extended position, showing the operative relationship; and

FIG. 8 is a longitudinal sectional view through the mobile base and turntable, showing the drive and steering connections through the turntable mounting.

DESCRIPTION OF THE PREFERRED EMBODIMENT The overhead service unit shown in the drawings comprises a low mobile base 10 which supports a turntable 12 on which is mounted a plural-section mast 14 which carries a traversing platform 16.

The base 10 is mounted on rear `drive wheels 18 and front steerable wheels 20, which may be -driven and steered in the manner shown in my prior Pat. N0. 3,095,- 945. Likewise, the turntable 12 may be mounted and driven in rotation in the manner disclosed in that patent.

The mast 14 as shown comprises four .mast sections which stand vertically in two parallel chordal planes at one side of the turntable. These include a fixed first section 21, a movable second section 22, a movable third section 23, and a movable fourth section 24. These are raised and lowered in unison, in a manner described below, by a hydraulic mast cylinder 26.

The fourth and outermost `section 24 of the mast forms a mounting for a vertically movable 7-shaped carrier 28 for the platform 16. This is raised and lowered along the outer face of the fourth section 24 of the mast by its own hydraulic platform cylinder 27.

'Ihe platform 16 comprises a peripheral frame 30 provided with a floor 32 and supporting a railing 34. The frame 30 is mounted on rollers on the horizontal leg 36 of the 7-shaped carrier 2-8 so that it can traverse lengthwise of itself on the carrier 28. As yshown in FIG. l, the platform 16 has a retracted position in which it is substantially centered over the base 10. In this position,

the platform can be lowered to a travel position well below the top of the collapsed mast 14, by lowering the carrier 28 on the mast section 24. The floor of the platform is provided with a trap door 38 which swings upward to the position shown in FIG. 1 -as the platform 1=6 is lowered over the upstanding mast 14. With the platform 16 in this travel position, a workman on the platform can operate the drive control and the steering wheel 40 to drive the unit as a whole along narrow aisles and below relatively low overhead obstructions, to a desired position of use. In such position the platform railing is below the top of themast, and the platform is low enough -to permit drive operation by a workman crouched below obstructions cleared by the mast.

From the travel position of the platform 16, such platform is raised above the mast by actuating the platform cylinder 27. In such position of the platform 16 above such mast 14, the platform can be traversed outward to the position Vshown in full lines in FIG. 2. The same horizontal traversing movement of the platform between centered position and extended position can be effected at any level to which the platform may be raised by extending the platform. In extended position, the platform 16 projects a substantial distance outward from the base, to permit a workman on the platform 16 to reach work areas well removed from the position of the base 10. IIn extended position, the platform may be lowered from its full line position in FIG. 2 to a lowered position shown in dotted lines at the bottom of FIG. 2,'by ac-tuating the platform cylinder 27 to lower the carrier 28 downward along the top mast section 24. In any position of extension or retraction, the platform can be raised by the mast 14 to a high level above the base 10, as shown in dotted lines at the top of FIG. 2.

To counterbalance the platform 16 -in its extended position, the opposite side of the turntable 12 carries a power-source battery 42, and may carry additional counter-balance.weights, so that a long platform extension can be used safely. The counterweights rotate with the turntable and the platform about the `axis of the turntable, so that the platform is counterbalanced and `stable in all positions of swinging movement.

The base is a generally rectangular structure having a top wall 50, and side walls 52. A large well 53 is formed in the base, defined by a circular 'side wall 54 which may be substantially tangent to the side walls S2. The side and end walls define downwardly open chambers in which the wheels 18 and 20 and the drive and steering .mechanisms are housed. The well has a bottom wall 56, below the tops of the wheels, and `such bottom wall 56 provides a base on which the turntable is supported by means of a central ring bearing S8 and peripheral rollers 60.

The turntable 12 is rotatably mounted in the well 53 and carries the service mechanism, including the mast d4, the battery and counterbalance 42, and appropriate hydraulic pumps and actuating motors for actuating the mast and the platform and for rotating the turntable. The turntable is a short cylindrical box-like structure having a bottomI wall 62,' a circular side wall 64, and a top Wall 66. The bottom Wall 62 contains a large central opening through which stands a hollow post 68 fixed to the center of the bottom wallv56 of the well. A turntable reaction sprocket 70 is mounted on this post within the turntable, Iand is engaged by a chain running from a drive sprocket 72 driven by a reversible turntable drive motor 74. Above the reaction sprocket 72, the post 68 supports a number of slip rings 76 which are respectively connected to wires running through an opening in the web of the sprocket 70 and downward through the central opening in the bottom wall 62 of the turntable 12 and through an opening in the bottom wall 56 of the well, for transmitting drive power from the battery 42 to the drive motors in the base. The slip rings 76 are engaged by contacts 718 (FIG. 6) mounted on a suitable post standing on the bottom wall 62 of the turntable.

For steering, the steering wheel 40 on the fixed m-ast section is connected by bevel gearing 82 to a shaft running downward to a chain sprocket -84 within the turntable. This is connected by a chain to a sprocket 86 mounted on a hollow shaft 88 journaled in the fixed post 68 and connected at its lower end to a sprocket90 engaged in a chain which controls the steering mechanism, which may be like that shown in my prior Pat. No. 3,095,945.

For drive and brake control, a thrust rod 87 is mounted within the hollow steering shaft 88. Downward movement of such rod actuates Ia brake and drive control lever 89 which controls the brakes and drive in the manner shown in my prior Patent No. 3,095,945. The thrust rod 87 is actuated by a suitable control treadle on the platform, connected by linkage which is effective when the platform is in travel position and ineffective when the platform is raised. In norm-al condition the brakes are set and the drive is de-energized, so that when the platform is elevated the base becomes immobile.

Actuation of the lift cylinders 26 and 27, the turntable motor 74, and the traversing drive motor 126 is controlled electrically by circuits which include control pushbuttons on a control panel on the platform.

As shown in FIG. 6, the fixed lower section 21 of the mast 14 comprises a pair of upright channel members 94 arranged in spaced parallel relation with their channels disposed toward each other. These are rigidly interconnected, and mounted in the turntable 12, supported by the bottomI Wall of such turntable, in a generally chordal plane between the fixed post 68 and the peripheral wall 64 of the turntable, with sufficient clearance for the other sections of the mast to be lowered into the turntable. The second section 22 of the mast comprises a pair of similarly arranged channel members 97, interconnected to form a rigid structure, nested within the first section, and suitably guided for vertical movement, as by rollers 98 in the channels of the uprights 94 of the first mast section. The mast lift cylinder 26 is mounted within the second mast section 22 and acts between the bottomof the first mast section 21 and the top of the second mast section 22.

The third mast section 23 comprises a pair of channel shaped uprights '102, interconnected to form a rigid structure, and mounted for vertical guided movement on the second section 22, as by means of rollers 103 riding in the channels of the second mast section 22 and connected to the third mast section 23 by brackets 104. The third mast section 23 stands in face to face relationship with the first mast section 21, in a generally chordal plane between such first mast section 21 and the peripheral wall 64 of the turntable, |as shown in FIGS. 6 and 8.

The fourthv mast section 24 comprises a pair of channel shaped uprights 106 interconnected to form a rigid structure and mounted for vertical guided movement in the third mast section as by rollers 107 engaged in the channels of that third mast section 23.

The platform carrier 28 comprises a vertical leg 108 mounted for vertical guided movement along the fourth mast section 24, as by means of rollers 109 engaged in the channels 106 of such fourth mast section and connected by brackets 1110 to the vertical leg 108 of the platform carrier 28. The platform lift cylinder 27 is mounted between the uprights of the fourth mast cylinder 106 and acts between the bottom of such mast section 106 and a crosshead 112 which carries a pair of chain sprockets 1'14 engaged in chains 116 connected between a fixed anchor point on the fourth mast section 24 and a fixed lift point at the bottomof the vertical leg '8 of the platform carrier 28. As seen in FIGS. 1 and 8, such vertical leg 108 in its lowered position lies substantially in abutting relation with the top wall 66 of the turntable 12.

As shown in FIGS. 4-6, the 7shaped platform carrier 28 has a horizontal leg 36 which includes two side rails 122 each of which carries a set of rollers 124 on which the platform is mounted for traversing movement with respect to the carrier 28. To actuate such traversing movement, the carrier 28 supports a drive motor 126 which acts through a gear reduction v127 to drive a transverse shaft 128 fitted at its ends with sprockets 129. Such sprockets 129 engage chains 130 stretched between end members of the platform to form sprocket-engaging racks on the platform. The chains are held in engagement with the sprockets by shoes 131. The chains and sprockets are located near the outer edges of the platform, as shown in FIG. 5, which provides clearance to allow the mast to project upward through the plane of the platform, and also serves to stabilize the platform against lateral sway or yaw relative to the carrier.

The platform, as shown in FIGS. 4 and 5, comprises a frame 30 having a pair of side rails 132 each of which includes inwardly projecting flanges 133 and 134 to dene an inwardly open channel for the reception of the supporting rollers 124 on the carrier and to provide a trackway for such supporting rollers in the longitudinal traversing movement of the platform 16. The floor 32 is supported from the side rails 132 and is suitably reinforced, as by stringers 136, which may underlie the edges of the door 38. The floor 32 covers the end sections ofthe platform and defines a central opening which is normally closed by the door 38. The door is hinged to one end section of the floor 32 and is opened by engagement of a roller 39 on the top section 24 of the mast as the platform is lowered over the mast.

The connections by which the mast is extended and by which the platform carrier 28 is raised on the top section 24 of the mast are shown diagrammatically in FIG. 7. The mast cylinder 26 acts between the base of the fixed mast section 21 and the top of the second mast section 22. The second section 22 carries at its upper end a chain sprocket 150, engaged in the bight of a chain 152 extending from an anchor point 153 on the irst mast section 21 over the sprocket 150 and to an anchor point 154 on the third mast section 23. Similarly, the third mast section 23 carries a sprocket 160 at its upper end which is engaged in the bight of a chain 162 extending between a fixed anchor point 163 on the second mast section 22 over the sprocket 160I and down to an anchor point 164 on the fourth mast section 24. With the four mast sections interconnected by these chains and sprockets as indicated, lift actuation of the mast cylinder 26 to raise the second mast section 22 will cause simultaneous lift movement of the third and fourth mast sections.

Movement of the platform carrier 28 vertically along the top mast section 24 is independent of extension movement of the mast sections, and is controlled by the platform cylinder 27. This acts between the base of the top mast section 24 and the crosshead 112, which carries sprockets -114 engaged in the chains 116 extending between an anchor point 115 on the top mast section 24 and an anchor point 117 at the lower end of the vertical leg 108 of the carrier 28. Extension of the platform cylinder 27 drives the chains to lift the platform carrier 28 from its lowermost position as shown in FIGS. l and 8 to its uppermost position as shown in FIGS. 4 and 7.

Operation is summarized as follows: With the platform in travel position as shown in FIG. 1, a workman on the rear section of the platform, to the left in FIG. 1, may operate the steering wheel `40, the brake and drive treadle (not shown) and the push buttons of the control panel on the platform, and is thus in complete control of the movements of all operating parts of the unit. From this position, the workman can release the brakes and actuate the drive motors to drive the unit to a work location and can steer the steering wheel 40. In such location, he can actuate the controls to raise the platform cylinder 27 and thereby lift the platform carrier 28 to a position projecting above the top of the top mast section as shown in FIG. 2. In that position of the carrier, he can then actuate the mast cylinder 26 to raise the platform to any desired level up to its maximum height shown in dotted lines at the top of FIG. 2. At any level above the lowered mast, the workman can actnate the traverse motor 126 to traverse the platform 16 from its centered position shown in FIG. 1 to its extended position shown in FIG. 3. With the platform 16 in its extended position, he can lower the platform cylinder 27 and thus lower the platform to its lowermost position as shown in dotted lines at the bottom of FIG. 2.

In any position of the platform, the operator can energize its turntable swivel drive motor 74 and rotate the turntable 12 and all the equipment carried by it, including the platform 16 and the counterbalancing battery 42 and weights, in either direction continuously through full circle rotation.

The overhead service unit of this invention is especially advantageous to perform overhead service work in crowded factory areas. It can move through narrow aisles to a position adjacent the work area. There the base can be stopped in a fixed position from which the platform may be raised straight upward past adjacent factory equipment and overhead obstructions. At any level, the platform can be rotated by rotation of the turntable for alignment in any direction from the base position. At any such level and in any direction, the platform may be traversed horizontally outward to a desired work position. The long traverse movement, combined with the permanent counterbalancing mounted with the platform on the turntable so that the counterbalancing is always effective, provides a long reach from the position of the base in any direction at any elevation. This combination provides highly versatile access to overhead work positions, of a character and range not provided by any prior overhead service unit.

I claim:

1. An overhead service unit, comprising a mobile supporting base, an upright plural-section extensible mast having a bottom section supported from the base and having a top section disposed toward the outside, the sections of said mast being retractable to a telescoped position of low height to pass beneath overhead obstructions,

a platform carrier mounted for vertical movement along said top section, between an upper position in which it projects above the top of the mast and a lower position substantially below the top of the top section and below the top of the mast when the mast is retracted,

a platform having a floor and mounted on said carrier for traversing movement of the platform longitudinally of itself between a retracted travel position in which t is substantially centered over the base to provide minimum overhang for travel along restricted paths, and an extended position in which it extends 7 substantially its entire length outward from the mast, the platform in said centered position being movable to the said lowered position of the carrier and having a door in its floor to pass the mast upward through the plane of the floor the platform being thereby positioned substantially below the top of the mast to clear overhead obstructions cleared by the mast, a turntable mounted for horizontal rotation on said base, said mast being mounted on said turntable, counterbalance means mounted on said turntable at the opposite side thereof from the extended platform to counterbalance the platform in extended position at all elevations of the platform relative to the vertical mast,

power means to raise the carrier to its said upper position Where the platform clears the mast for traversing movement,

power means to extend the mast to raise the plaform to overhead work positions,

drive means for rotating the turntable with the platform at any level,

and drive means to traverse the platform in such mast clearing position at any level above the lowered mast and in any position of the turntable.

2. An -overhead service unit as in claim 1, further comprising side rails on the platform having horizontally disposed anges,

supporting guide means on the platform carrier supporting said anges for longitudinal movement for o traversing the platform, platform dioor sections extending between said side rails at the ends thereof, said door being between said sections, said sections providing areas on which a workman may stand, the area at the inner end of the extended platform being a drive area which, when they platform is centered and lowered over the mast, is disposed to overlie the turntable at the inner side of the mast. 3. An overhead service unit as in claim 2, further comprising control means including steering means mounted on the inner side of the mast in position `to -be operated by a workman standing in said drive area. 4. An overhead service unit as in claim 1, further comprising a railing standing upward from said platform about the periphery thereof, of suicient height to retain a workman thereon, the platform in travel position being suiciently below the top of the mast to dispose said railing below such top. '5. An overhead service unit as in claim 3 in which the platform in lowered travel position is sufficiently below the top of the mast to `permit a workman thereon to operate the controls While crouched beneath an overhead obstruction cleared by the mast.

6. An overhead service unit as in claim 1, further comprising a platform frame having side rails spaced a suicient distance to clear said mast as the platform is lowered over the mast, the platform carrier lbeing at the outer side of the mast and having supporting guide means thereon supporting said side rails for longitudinal movement for traversing the platform between said retracted and extended positions. 7. An overhead drive unit as in claim 6, further comprising a platform traversing drive including a pair of drive gears xed to a common traverse shaft on said platform carrier, a rack-like element mounted at each side of the platform and engaged by said drive gears, and a reversible drive for driving said common shaft. 8. An overhead service unit as in claim 1, comprising a well formed in the base, in which said turntable is mounted, the turntable mounting including a central xed portion about Which the turntable rotates and through which controls are connected between the turntable and base,

a fixed mast section comprising a pair of spaced uprights mounted on the turntable in a rst chordal plane between said iixed mounting portion and the periphery of the turntable,

a movable mast section supported from saidfixed section in a chordal plane between said first chordal plane and the periphery of the turntable and at the outer side of the fixed section,

the platform carrier being supported from said movable mast section and disposed at the outer side of said movable mast section,

said platform carrier having an outwardly extending portion for supporting the platform in extended position wholly outside the outer face of the mast.

References Cited UNITED STATES PATENTS 2,753,224 7/ 1956 Troche 182-63 3,031,027 4/ 1962 Mitchell l82-62.5 3,095,945 7/1963 Mitchell 182--148 3,437,174 4/ 1969 Coblenz 182-141 REINALDO P. MACHADO, Primary Examiner U.S. C1. X.R. 

